After several years of good service as a sub amp, my Leach amp began to produce a low-level hum in one channel. This hum continued to develop and increase to unbearable levels. I've replaced the diode bridges (dual mono) with no improvement. I know I have a problem...with no input signal, the affected channel drives the woofer cones to full extension (outward) along with a hum. Looks like a DC signal to me. What should I check, the ouput transistors? And how?
Thanks